1. Field of the Invention
The present invention relates to a content delivery system.
2. Description of the Related Art
Recent advance in communications technology has enabled user communications terminals including mobile terminals to be provided with diversified non-data as well as data communication functionality. This tendency has culminated in the proliferation of content delivery systems.
As a content delivery system, the location based services system is currently receiving attentions for serving mobile terminals. In the location-based services, the mobile terminal transmits its location information, for example, identifiers of base stations the mobile terminal is currently attached to and field strength data to the content server. In response, the content server formulates a content based on the mobile terminal's current location and delivers it to the mobile terminal. The GPS (global positioning system) is also used in mobile terminals to obtain location information when a mobile terminal accesses a content server.
Computer game terminals provided with communication capability are another example of recently developed communication modes. For serving this type of communication devices, a content delivery system is contemplated in which users access a computer game program maintained in a game server and the computer game terminal control its scenario by sending the position, speed and tilt information of the terminal to the gate server.
What is common to these content delivery systems is that the user terminal is provided with means to extract its own operating conditions and the information about its user and request a content from a content server using parameter data representing such operating conditions and user's information. In response, the content server formulates a content based on the parameter data supplied from the user terminal, and transmits it to the requesting user terminal.
In prior art content delivery systems, when the user terminal requests a content from a content server, it automatically acquires parameter data specified by the user and transmits it to the content server. However, if the content server is not operating or if the requested content is not included in a service list of contents, or if the transmitted parameter data does not contain information necessary to generate a content, the requested content cannot be delivered to the user terminal. In addition, from the viewpoint of user's privacy, a system is contemplated in which parameters are exchanged between the user terminal and the content server under certain conditions for authentication.
Therefore, the prior art content delivery system, parameter acquisition is performed even when a content is not retrievable from the content server. If the parameter data is user's location information and the location information is acquired from GPS receiver of the user's terminal, it is necessary to perform calculations on signals received from GPS satellites, which consumes a substantial amount of power and such consumption of battery power is an important consideration. This applies to a mobile terminal which retrieves location information from the mobile network position data service facility. From the power savings viewpoint, it is undesirable to perform parameter acquisition regardless of whether a content can be retrieved from the network.